1. Field of the Invention
The present relates to a laser output end device, and more particularly, to a fiber laser device.
2. Description of Related Art
Fiber laser device is first proposed in 1964, the power thereof is several milli-watts. In conventional fiber laser device, laser diode serves as an exciting pump, optical fibers used in conventional fiber laser device are a kind of single cladding fibers, and laser beam is directly coupled to and transmitted in the core of the optical fiber. Usually, the composition of the core is plastic or glass. Since the transmission of optical fibers is not interfered by electromagnetic wave and has few decay, optical fibers are gradually applied in various fields.
Recently, due to the double cladding fibers are proposed and enhancement of photoelectric transduction efficiency, the power of fiber laser devices increases rapidly year by year. Nowadays, high power fiber laser devices having several kilowatts (KW) is already developed.
High power fiber laser devices have gradually become the mainstream product in the market. In order to ensure that high power fiber laser devices can output stably, a real time power measuring system for monitoring output of the fiber laser devices is required.
In one prior art, in order to measure output of fiber laser devices, an optical sensor for measuring output of fiber laser devices is installed at a laser output end of fiber laser devices. In another prior art, in order to measure output of fiber laser devices, a beam splitter is installed at a laser output end of fiber laser devices to split the laser beam into two split beams, and an optical sensor is installed on light-transmission path of one of the split beams. In this way, output of fiber laser devices can be measured. Detailed descriptions regarding the prior art measurements are provided below with reference to FIG. 1 and FIG. 2.
FIG. 1 schematically illustrates a cross-sectional view of a conventional fiber laser device. Referring to FIG. 1, a conventional fiber laser device 100 includes a laser pump (not shown), an optical fiber 102, and an optical sensor 104, wherein the optical fiber 102 further includes a core 102a and a cladding layer 102b, and the core 102a is wrapped by the cladding layer 102b. 
As shown in FIG. 1, in order to estimate the overall power of the fiber laser device 100, a portion of the cladding layer 102b of the optical fiber is stripped such that a notch A shown in FIG. 1 is formed. An optical sensor 104 is then disposed at the notch A to measure power of the fiber laser device 100 irradiated from the notch A. The overall power of the fiber laser device 100 can be estimated in accordance with power of the fiber laser device 100 irradiated from the notch A. The overall power of the fiber laser device 100 can be modified in accordance with the measuring result (notch A) so as to stabilize the overall power of the fiber laser device 100. However, the optical fiber 102 is damaged when a portion of the cladding layer 102b of the optical fiber is stripped. The optical signal transmitted in the core 102a is decayed and the overall power of the fiber laser device 100 is reduced accordingly.
FIG. 2 schematically illustrates a cross-sectional view of another conventional fiber laser device. Referring to FIG. 2, a conventional fiber laser device 200 includes a laser pump (not shown), an optical fiber 202, an optical sensor 204, and a beam splitter 206, wherein the optical fiber 102 includes a first optical fiber 202a and a second optical fiber 202b; a laser beam 208 is irradiated by the laser pump; the beam splitter 206 is disposed between the first optical fiber 202a and the second optical fiber 202b so as to split the laser beam 208 into a first laser beam 208a and a second laser beam 208b. Additionally, the optical sensor 204 is disposed on light-transmission path of the second laser beam 208b so as to measure power of the second laser beam 208b and estimate power of the first laser beam 208a. The overall power of the fiber laser device 200 can be modified in accordance with power of the second laser beam 208b so as to stabilize the overall power of the fiber laser device 200.
In the measurement shown in FIG. 2, not only the optical fiber 202 is damaged, but also the laser beam 208 is split into the first laser beam 208a and the second laser beam 208b. Additionally, the fiber laser device 200 only output of the second laser beam 208b. In other words, the overall power of the fiber laser device 200 is reduced because the overall power of the fiber laser device 200 is equal to power of the second laser beam 208b. 